In German Patent Document No. DE-OS 28 21 650, an apparatus of the latter type is described which comprises a spreading device having two spreading rollers extending across the path of the web on opposite sides thereof and engaging the opposite surfaces of the web, each of these rollers having threadlike formations, hereinafter referred to as threads, of a different hand or screw sense so that upon rotation of the rollers, the helical rib or thread on one longitudinal side of the web of each roller draws the material away from the center while the thread of the opposite hand on the same roller draws the material on the opposite longitudinal side of the roller away from the center to thereby draw out laterally or "spread" the web of material.
The guide device provided downstream of the spreading device is constituted as a unit independent of the spreading device.
This downstream unit comprises two spaced apart parallel guide rollers around which the web is partially slung and which are mounted in a frame fixed on guide members which are guidable in converging straight guides lying parallel to the plane of the fabric and converging in the fabric travel direction.
The guide parts in the respective guides are so connected together by the frame carrying the rollers that a swing-shifting movement of the rollers when the guide parts are displaced is possible.
That means that the rollers which extend across the width of the fabric can be so inclined that different inclinations can be established for appropriate correction to the respective side.
A drawback of this device is the large spatial requirement for the device, since guides on both sides of the fabric web are required and because considerable free space will be provided laterally of the frame carrying the two rollers, since the rollers may have to be shifted considerably to each side and appropriately swung as part of their adjustment movement.
Swing-shifting roller arrangements, moreover, require a large number of parts, complex assembly and expensive control and maintenance procedures.
Indeed, where limited space is available, this type of guide unit cannot be used and this is important because such devices frequently are desirable in housings in which the fabric is treated and which have only limited lateral space. A further disadvantage of the aforedescribed apparatus is the fact that it occupies considerable space in the longitudinal direction as well because of the inclined guides and the drive for the guide members thereby requiring that the guide unit be located relatively far from the spreading unit.
A large separation between the two units entails the danger that the spreading effect may have ended at an edge region of the fabric before the fabric enters the guide device so that folds may be created or that the edge may pull inwardly, thereby defeating the purpose of the spreading unit or detrimentally effecting guidance.
It is known in practice to provide the spreading spindles so that they engage only the edge regions of the fabric and to provide each of the threadlike spreading spindles with a web guide which comprises a pair of rollers gripping the edge region of the goods. This combination has the drawback that holes or tears in the goods can be generated by the threaded spreading spindles or can detach on the guiding spindles to the detriment of proper advancement of the web.
Furthermore, with such systems, it is possible for the edges of the web to spring suddenly inwardly or to pull out from the spreading and guide device upon a tear of the fabric. The fabric can also jump out of the feed plane which must lie precisely between the two rollers.
The goods lie with a slight looping around the upper or lower rollers of the web guide. An automatic threading of the web through the spreading and guide device is not possible, since the goods tend to be pulled to one side or the other. In operation, the apparatus may be turned off completely and the web threaded through the apparatus by hand in a time consuming operation.